Electrical circuits for radioreceivers



Feb. 17, 1931. s. BALLANTINE 9 ELECTRICAL CIRCUITS FOR RADIORECEIVERS Original Filgd June 1'7, 1924 STUART BAL'DA N' IIN 'E, on MoUN'rAiN- LAKES, ,NEW (JERSEY, 'ASSIGNOR TO RADIO FREQUENCY LABORATORIES, INCORPORATED, or ZBOONTON, NEW-JERSEY, A con- .PORATION OF NEWJERSEY ELECTRICAL oIaoUr'rs FOB RADIORECEiVERS Original application filed'iune 17, 1924, Serial No. 720,708. latent No. 1,760,871, dated June 3, 1930. Divided. and 'this application filed March 10.;1928, Serial No. 260,779.

Thisapplication is a division ofmy co-.

pending application Serial No. .7 20,708, filed June 17 ,1924, 3, 1930.

to electrical circuits adapted to reduce v or suppress undesired effectsdue to capacitive coupling existing between the anode and the control electrodeof a vacuum tube, or input currents, the. introduction into one of the audion circuits of sufficientresistance to renderthe stage stable, or the use of untuned or aperiodic circuits.

An object of the present invention is to provide an amplifier stage which will suppress the eifects of retroactive currents over an extended range of frequencies. More specifically an object of the invention is to pro vide improved forms of anti-regenerative C11? cuits llLWlllCh thepath taken by the retroactive, currents and/or thecompensati ig currents includes a resistance.

These and other objects of the invention will be apparent from the following specification when :takenwith the accompanying drawings, in which I r Fig. 1 is a circuit diagram showing an audion repeater element with arrangements for rendering. it. unidirectional, the effects of capacity coupling being eliminated. by a compensation method;

i Fig. 2 is a'circuit diagram showing an audion repeater-element with arrangements for I rendering it unidirectional, the effects of capacity coupling being eliminated by a neutralization method;

audion repeater element with arrangements for rendering it unidirectional, theeiiects of Patent 1,760,871 granted June The present application relates especially Fig. 3' is a circuit diagram showing an capacity coupling being eliminated by a mod ified neutralizationmethod. I In the circuit shown in Fig. 1, the general method employed to compensate for the ef-' fe'cts' of capacity coupling has been described 'my my copending application, Serial No.

629,702, filed April 3, 1923.

L and L 'constit'ute the input transformer tuned by means of the variable condenser C Any other suitable input arrangement may be made. The output transformer is formed by L and L which are tuned by C The circuits may be energized from any suitable source such as the usual A, B andG batteries or the like. A filament control resistance R is included in the filament circuit and may also'serve in biasing the grid negatively. A filament shunting condenser of low impedance, 0 may be connected across the filament terminals to introduce alternating current plate current through both filament tenninals represents a compensating capacity which may obviously reside between the electrodes of the audion or their connecting wires or in an external condenser.

The undesired coupling between the input circuit and the output circuit arises,'in part at least, from the capacity Cm. As described in my copending application, Serial No. 629,702, the efi'ects of such capacity coupling may be reduced or eliminated by bringing Y point Y of the input circuit to the alternating current potential of a point X in the output circuit. "Point Yis the lowerterminal of the input c rcuit, that is, the, terminal having the lower alternating current potential, "or, in

general, most closely approaching to the alternating current potential of' the filament. The lower terminal ofthe input'circuit is brought to the potential of point X by means of an extra windingor coil L which is inductively coupled to the plate impedance L for example, at the lower end thereof, as shown.

In certain cases it is desirable to add com pensating resistances R and R to either Gm or C or both, either inseries, as shown in Fig. 1, or in parallel..

In Fig. 1 the upper circuit may thus be connected to the filament throughthe serially connected resistance R terminal of the input and capacity C and to the audion grid through resistance R The network has the form of an alternating current iVheatstone brid e which, when balanced, operates to counteract the effects of retroactive currents flowing to the grid and the input circuit through capacitive coupling between the output and inputcircuits such as the capacity. Cm. A compensating current is impressed upon the lower terminal Y by the added winding L The compensating resistance R R may perform several functions, and, according to the constants of other elements of the amplifier stage, any or all of the effects of these resistances ma be important in any particular circuit. These resistances may effect an adjustment of phase relation between the retro: etive currents and the compensating currents, and they may also compensate for the resistance component of the variable space charge coupling. The resistance R may also function as a losser, since it is serially connected between the tuned input circuit and the grid on the audion.

Fig. 2 illustrates a repeater unit in which the audion capacity coupling is eliminated by a neutralization method. The principle of such methods is disclosed in my copending applications, Ser. No. 629,702, filed April 3, 1923, and Ser. No. 167,701, filed February 12, 1927. Referring to Fig. 2, L, and L constitute the input transformer which is tuned .by the condenser C C is a compensating condenser; L and L are either separate coils or parts of the same coil; L and C represent the output circuit; R, is a compensating resistance; R is a resistance in the filament circuit, the direct current drop across which is used to give the grid a suitable negative bias; the C battery reinforces the biasing effect of R,- the A and B batteries have their conventional circuit locations; C is a filamentshunting condenser of low impedance. The output circuit, represented by the coil L must be coupled to L and L so that the effective impedances between the terminals of L and L, are of proper value to maintain a state of balance in the circuit, obviously also the coupling between L L and L must be fixed. It is not necessarv that L and L, be

P coupled together, but their couplings to L,

must result in impedances between their ter minals which satisfy the requirements of neutralization. F or best results, with tubes of the usual 15,000 ohms plate resistance, as now constructed, the coil L and L are of small inductance compared with that of L and the coupling between L and L and be tween L and L, should be close. In order that persons skilled in the art may reproduce my results, I give the following constants of one specific circuit: L microhenries; L,==20 microhenries; L v 300 microhenries; C 0.O0033 micrafarads; 650000005 microfarads. These values were found suitable for a unit designed to cover. a wave length range of 200 to 600 meters.

Fig. 3 illustrates a repeater unit in which an alternative method of neutralizing the audion capacity coupling is employed. This method is disclosed in my copending applications above referred to, and in substance in Hazeltime U. S. Patent 1,et89,228, April 1, 1924. The other arrangements for eliminating the enumerated couplings other than that due to the audion capacity, are those already described. L and L are two coils of preferably tight coupling wound in opposite directions and so connected that their non-common terminal voltage are opposite in phase; Q. is a compensating condenser; R and R are compensating resistances, which make up the departure ofthe voltages of L and L from exact 180 phase relationship and which also compensate for the resistance component of variable space charge coupling; R is a filament resistance, the drop across which helps to bias the grid negatively; the battery C also has this function; C is a fiilament-shunting condenser of low impedance; the batteries A and B have their conventional functions; L and L, constitute the output transformer, tuned by the condenser C Various modifications of the specific circuits herein described, and equivalent arrangements thereof, fall obviously within the scope of my invention. For example, arrangements in which the compensating or phase-adjusting resistances are wholly or partially embodied in one or more elements of the compensating circuit, as the co1npensating inductance or capacity, are contemplated by me, and fall within my invention; Moreover, my invention extends to the control of the resistance balance of the circuit in either direction, and is not limited to a Cll" cuit which is perfectly balanced.

I claim:

1. An electrical amplifier circuit comprising, in combination. a vacuum tube including at least anode, cathode, and control electrode elements; a tuned input circuit for said vacuum tube; an output circuit for said vacuum tube; a connection including a resistance between the high potential terminal of said input circuitand the control element of said vacuum tube; and means operative to reduce the effects of retroactive currents due to coupling between said input and output circuits.

2. An electrical amplifier circuit comprising, in combination, a vacuum tube including at least anode, cathode, and control electrode elements; a tuned input circuit for said vacuum tube and an output circuit therefor, said circuits having capacitive coupling between them; a resistance connected between the high potential terminal of said input circuit and the control electrode of said vacuum tube; and compensating means operative between sald input and output cir= cuits and including a coil electromagnetically coupled to a 0011 in one of said circuits and coupled to the other of said circuits by capacitive lmpedance.

3. An electrical amplifier circuit comprisin the reverse sense to a coil in one of said circuits and coupled to the other of said circuits by capacitive impedance. V

i. An electri al amplifier circuit comprising, in combination, a vacuum tube including at least anode, cathode, and control electrode elements; a tuned input circuit for said vacuum tube and an output circuit therefor, said circuits having capacitive coupling between them; a resistance connected between the high potential terminal of said input circuit and the control electrode or said vacuum tube; and a compensating circuit including a coil electromagnetically coupled in the reverse sense to a coil in one of said circuits and capacitively coupled to the other of said circuits.

5. An electrical amplifier stage comprising a vacuum tube, a tuned input circuit and an output circuit having capacitive coupling between them, a compensating circuit including a. capacity and inductance connected in series between said input and output circuits, and a resistance connected between the high potential terminal oi said input circuit and the grid of said vacuum tube.

6. An electrical amplifier circuit comprising, in combination, a vacuum tube including at least anode, cathode, and control electrode elements; a tune-d input circuit for said vacuum tube and an output circuit therefor, said circuits having capacitive coupling between them; a resistance connectedbetween the high potential terminal oi said input circuit and the control electrode of said vacuum tube; and acompensating circuit including a C'Oll electromagnetically coupled in there' verse sense to a coil in said input circuit and capacitively coupled to a point in said output circuit. 1 V

7. An electricalamplifier circuit comprising, in combination, avacuum tube including at least anode, cathode, and control electrode elements; a tuned input circuit for said vacuum tube and an output circuit therefor, said circuits having capacitive coupling between them; a resistance connected between the high potential terminal of said input circuit and the control electrode of said V vacuum tube; and a compensating circuit connected between said input and output circuits and including, in series, a coil electromagnetically coupled in the reverse sense to a coil in said input circuit, a capacity and a resistance.

8. An electrical amplifier stage of the type which includes a vacuum tube and tuned input and output circuits associated therewith having coupling therebetween whereby undesired retroactive currents are setup, and in which the effects oi said retroactive currents are opposed by additional currents flowing between said input and output circuits; characterized by the fact that a resistance is connected between the high potential terminal of said input circuit and the control element of said vacuum tube.'

9. An electrical amplifier stage of the type which includes a vacuum tube and tuned input and output circuits associated therewith having coupling therebetween whereby undesired retroactive currents are set up, and in which the effects of said retroactive currents are opposed by additional currents flowing between said input and output circuits; characterized by the fact that a resistance of such value as to produce an adjustment of phase relation between said retroactive currents and said additional currents is connected between the high potential terminal of said input circuit and the control element of said Vacuum tube.

10. An electrical amplifier circuit comprising, in combination, a vacuum tube including at least an anode, a cathode, and a control electrode; a tuned input circuit including an input transformer having a tuned secondary winding associated with said cathode and said control electrode; an'output circuit including anoutput transformer having a primary winding associated with said cathode and said anode and a tuned secondary winding; a resistance connected in series between the high potential terminal of said tuned secondary Winding of said input transformer and said control element of said vacuum tube; and compensating means associated with said input and output circuits and including capacitive impedance arranged to permit the flow of anti-regenerative currents of such phase and amplitude as to oppose regenerative currents flowing through inherent capacitive coupling between said input and output circuits.

In testimony whereof, I aflix my signature.

' STUART BALLANTINE. 

